Premium Bonds Odds Calculator
See the expected annual winnings on your Premium Bonds holding, an honest median (typical) outcome, your monthly odds of winning anything at all, and how it stacks up against an ordinary savings account.
Estimate only. Estimates only, based on the prize rate and odds you enter, not financial advice. Premium Bonds are provided by NS&I; verify current rates, odds and limits at nsandi.com before making a decision.
Enter your holding
Your expected winnings, a realistic median outcome, and a comparison against a savings account appear here as you type.
How this is worked out
NS&I Premium Bonds pay no interest. Instead, the whole "prize fund rate" is distributed as tax-free prizes in a monthly draw, and every eligible £1 Bond number has the same published odds of winning. The "expected annual winnings" figure above is simply your holding multiplied by the prize fund rate, the same maths as ordinary interest, and the number NS&I itself quotes. But it's a statistical average across millions of Bond numbers, not what a typical holder actually experiences: a small number of huge prizes (including the monthly £1 million jackpots) pull the average upward, so the typical (median) holder tends to win somewhat less than the average in any given year. We show an approximate median, roughly 85% of the mean for a mid-size holding, alongside the mean so you can see both sides of the picture. We also calculate the exact probability of winning at least one prize this month, using the standard "independent draws" model: with n Bond numbers each having a 1-in-N chance, the probability of winning nothing is (1 − 1/N)^n, so the probability of winning something is 1 minus that. Larger holdings have many more Bond numbers in the draw, so their results track the advertised rate far more reliably than a small holding's.